The present invention is related to the detection of angular motion. Specifically, an magnetohydrodynamic MHD sensor is provided which will sense the presence of angular displacements which result from a shock force being applied to a platform supporting the sensor.
Motion sensors have been developed in the past for sensing low frequency angular displacements. One such sensor is described in previous U.S. Pat. No. 5,067,351, which is especially suitable for measuring low frequency angular displacements. The device described in the foregoing patent is an MHD motion detection sensor with electronic circuitry for providing an amplified sensor output signal representing the angular velocity experienced by the device.
Although the foregoing patented device performs particularly well at low frequency angular measurements, the space requirements for this device are too great for many applications. Further, the device cannot meet the need for greater sensitivity at higher angular motion displacements which is necessary for some applications.
One such application is the detection of shock forces. In certain electronic systems employing magnetic disk drives, it is important to protect the magnetic disk drive against the consequences of an unexpected shock force being applied to the system. The shock force may displace the magnetic head into an adjacent track of a disk at a time it is writing data, resulting in data being written to an inappropriate place on the disk, destroying any data previously written to the affected location.
Experience has demonstrated that to successfully detect the presence of a shock force applied to such systems requires the capability to measure angular displacements which occur in frequencies above several hundred Hertz. Further, such sensing devices must fit within the size constraints imposed by the system being protected.
The present invention overcomes these difficulties to a degree not possible with the device of the foregoing U.S. patent.